Asphalt and process for producing the same



March 1o, 1942'. D, E, CARR 2,276,155

ASPHALT AND PROCESS FOR PROUUCING THE SAME Filed Feb. '7, v1939 2Sheets-Sheet l @me 59g. f.

March 10, 1942.

ASPHALT AND PROCESS -FOR PRODUCING THE SAME Filed Feb. "7, 1939 Crade D.E. CARR 2 rSheets-Shea?l 2 INVENTOR.

Donald E. Carr Patentes Mar. 1o, 1942 narran star ASPHALT AND PROCESSFOR PRODUCING THE SAME Donald E. Carr, Los Angeles, Calif., assignor toUnion Oil Company of California, Los Angeles, Calif., a corporation ofCalifornia Application February' 7, 1939, Serial No. 255,084

9 Claims.

This invention relates to a process for the manufacture of asphalts,particularly air-blown or oxidized asphalts.

It is an object of my invention to improve the air-blown characteristicsof asphalts and their stability to weathering.

It is another object of my invention to improve the characteristics ofthe charging stock from which the oxidized asphalt is produced. Otherobjects of my invention will appear from the following description.

It is well known in the art of manufacturing air-blown asphalts thatsuch products may be prepared by blowing the charging stock with air orother oxygen containing gases at an elevated temperature and that theresulting oxidized asphalt will possess desirable low temperaturesusceptibilities, high melting point for given penetration andmoderately high ductilities. The charging stock generally employed is atopped residuum obtained from an asphalt base crude oil.

It is generally recognized in the asphalt industry that the nature ofthe charging stock used in the manufacture of air-blown asphalt has avery marked effect on the properties of the air-blown product. Somecharging stocks produced from certain selected crude oils oxidize tobetter asphalts than charging stocks produced from other crude oils. l

I-Ieretofore, very little was known concerning the nature of thereactions occurring during the blowing process of what factors wereresponsible for the high or low quality of the resultant airblownproducts. I have now discovered thatby means of proper solventfractionation, asphaltic materials may be separated into threecomponents, namely, asphaltenes, resins and oil. In this specificationthe term asphaltenes is defined as those components of topped residuumwhich are insoluble in propane and insoluble in petroleum ether. Theterm resins includes those constituents of topped residuum which areinsoluble in propane but soluble in petroleum ether. Oil comprises thosematerials present in topped residuum which are soluble in both propaneand petroleum ether. By the term topped residuum is meant thosematerials derived from crude oil by the removal of the more volatilefractions up to and including at least the gas oil fraction thereof. Aportion of the lubricating oil may also be removed by distillation.Furthermore, it is intended to include those naturally occurringasphaltic materials, such as Trinidad asphalt.

I have discovered that during the air-blowing process for producingoxidized asphalts from residua the oil fraction of the asphalt remainssubstantially unchanged in amount except for distillation losses butthat the proportion of the resin fraction decreases progressively as thelength of air-blowing increases, the resins apparently being polymerizedto form materials of the class of asphaltenes and that consequently theproportion of asphaltenes in the finished product is increased over thatpresent in the residuum prior to air-blowing. Furthermore, I havediscovered that the asphaltene fractions of various residuum arerelatively stable to weathering whereas the resins and particularly thelighter resins are relatively unstable to weathering and tend to formoxidation products upon exposure to light in the `presence of oxygen. Ithas already been determined that thel lighter lubricating oil fractionsalso give rise to instability of air blown asphaltic materials but thatthe relatively heavy lubricating oil fractions are similar to theasphaltenes insofar as stability to weathering is concerned.

As the result of the above discoveries I have been able to produce asynthetic asphaltic residuum which can lbeoxidized in a fraction of thetime heretofore required for naturally occurring residuums to produceair-blown asphalts of unusually high stability as regards weathering.These desirable objects are accomplished by Kseparating the asphalt intofractions comprising asphaltenes, resins and oil an-d subsequentlyblending the oil with the asphaltenes in desirable proportions to yieldan air-blowing stock already possessing mildly air-blown characteristicswhich are improved to any desired extent by only a short period ofoxidation with air or other oxygen containing gas. By this process itwill be noted that the resin fraction, which represents the unstableportion of asphaltic material, and the conversion of which toasphaltenes represents the time consuming process in the air-blowing ofnaturally occurring residua has been eliminated. In practicing thisinvention I have found it desirab-le to conduct the separation ofasphaltenes from the residuum in such a manner that a portion of theheavier more stable resins are separated with the asl phaltenes in orderto act as plasticizers for the latter material in order that it may besubsequently more readily admixed with the oil fraction separated fromthe residuum.

In general, the separation of the charging stock intok asphaltenes,resins and oil mayA be accomplished in a number of ways. According toone method, the asphalt residuum may be first extracted with a solventadapted to disssolve all of the oil and to precipitate substantially allof the asphaltenes and resins. The precipitate is then extracted with asolvent adapted to dissolve substantially all of the resins and toprecipitate all of the asphaltenes. Theasphaltenes and the oil may thenbe `blended in the desired proportion to produce a composited asphaltwhich may be oxidized to the desired characteristics.

In another method, the asphalt residuum may be rst extracted with asolvent adapted to dissolve substantially all of the oil and resins andto precipitate all of the asphaltenes as a resin free fraction. The oiland resin mixture may then be extracted with a solvent adapted todissolve substantially all of the oil and to precipitate the resins.Again the asphaltenes an-d the oil may be blended in the desiredproportion to produce the composited asphalt which then may be furtheroxidized to the desired characteristics.

The process may be better understood by reference to the drawings whichrepresent schematic ow sheets for carrying out the process. According toFig. 1 of the drawings, an asphalt-containing crude oil is rst distilledand steam topped with or without vacuum to distill at least all of itsgas-oil content. The still bottoms or the asphalt residuum is thenextracted with a solvent which is adapted to dissolve substantially al1of the oil but which will precipitate all of the asphaltenes and resins.Solvents capable of effecting this separation are the liqueiied normallygaseous hydrocarbons such as ethane, propane, butane, iso-butane, andsometimes pentane, or mixtures thereof. Such hydrocarbons are obtainedby rectification of casinghead gasoline by the so-called stabilizingmethod now conventional in the natural gasoline industry. They comprisethe overhead gaseous fractions of the stabilizing process. The gaseousfractions are liqueed by compression and cooling in the conventionalmanner and are drawn oir into pressure chambers where they aremaintained in the liquid state until they are used. The necessarypressure to maintain propane, for example, in a liquid state, isapproximately 125 lbs. per square inch at about 75 F. Of course, theextractive power of the solvent may be varied by varying the conditionsof extraction, for example, the temperature of extraction andthe amountof solvent. In the drawings, I have shown the extraction of the oil fromthe asphaltenes and resins as being carried out with the use of propane.In this case, the residuum is mixed with about 3 to 6 volumes of propaneat a pressure of about 125 lbs. or upwards, preferably at a temperatureof 100 F. and the mixture is allowed to remain in a quiescent stateuntil the precipitated asphalt and resins have settled to the bottom ofthe container. The clear supernatant solution of oil and propanesubstantially free from resins is then decanted and subjected todistillation to remove the propane which may be recovered by compressionand cooling and returned for further treatment of residuum. Dependingupon the degree of topping of the crude oil, the oil may at this pointbe fractionally distilled to remove light lubricating oils since thevolatility of an asphalt essentially determines its weatheringdurability or storage stability. The evaporation of oils from asphaltover a period of time results in embrittlement, cracking, checking, etc.However, these oils may be removed in the initial topping of the crudeoil so as to leave only high molecular weight oils in the residuum.

The precipitate ofasphaltenes and resins is then extracted with asolvent which is adapted to dissolve the resins and to precipitate theasphaltenes. It is desirable, however, to control extraction conditionsand/or solvent to leave the heavier resins with the asphaltenes. Forthis purpose, I may employ such solvents as petroleum ether or a mixtureof butane and iso-pentane or a mixture of naphtha and propane. In thedrawings, the asphaltene-resins mixture is extracted with about 3 to 4volumes of petroleum ether at a temperature of about 175 F. to effectthe separation of resins from asphaltenes. The precipitate ofasphaltenes containing preferably the heavier resins is next subjectedto distillation to remove petroleum ether. The bottoms are then blendedin the desired proportion with the resinfree oil previously separatedfrom the residuum. The blend is next subjected to oxidation with air orother oxygen containing gas for a short period of time to oxidize theblend to the desired 1inished product.

In Fig. 2 of the drawings, the residuum produced as in Fig. 1 is firstextracted with the solvent which is adapted to dissolve substantiallyall of the oil and resins, preferably only the lighter resins and toleave the asphaltenes and preferably the heavier resins as anundissolved precipitate. For this purpose, petroleum ether or a mixtureof butane and iso-butane or a mixture of propane and naphtha may be usedas described in connection with the process of Fig. l. The solvent, inthis case, petroleum ether, is then stripped from both the solution andthe precipitate.

The oil containing the undesirable resins, i. e. the light resins, isthen extracted with a solvent adapted to precipitate all of the resinsfrom the oil. This may be accomplished by means of propane or any of thesolvents described in connection with the irst extraction step oi theprocess of Fig. 1 employing approximately 3 to 6 volumes of propane toone of the oil at a temperature of F. and under a pressure of upwards of125 lbs. per square inch. The propane is then stripped from the oil andalso the resins. The oil may then be blendedwith the separatedasphaltenes in the desired proportion and the blend may be air-blownwith air or other oxygen-containing gas to the desired grade as in Fig.1.

Thus, in the description of the drawings, there are two methods forarriving at substantially the same result. To summarize, in one methodthe undesirable resins are precipitated along with the asphaltenes andare subsequently removed from the asphaltenes whereas in the other, theundesirable resins are extracted with oil and are subsequentlyprecipitated from the oil. As stated previously, it is desirable tocarry out the processes so that the heavier resins remain with theasphaltenes so that when the two fractions are blended in the desiredproportion a certain amount of high molecular weight resins remain withthe composited asphalt to serve as plasticizers in the blending of theasphaltenes with the oil. rlhese resins are converted into stableasphaltenes when the blend is subjected to airblowing.

The following is submitted as a specific example of my invention which,however, is not to be considered as limiting but merely as illustrativeoi' the invention.

A Santa Fe Springs crude oil was subjected to vacuum distillation at atemperature of about 675 F. to produce a still .bottom having a meltingi point of F. and a penetration of 6 at 77 F. 70

These bottoms were then extracted at F. with 350 volume percent of asolvent mixture composed of 80% butane and 20% iso-pentane to produceapproximately 65.5% by weight of an v insoluble asphaltene fractioncontaining heavy resins having a melting point of 220 F. and apenetration of one at 77 F. and approximately 34.5% by weight of asoluble oil fraction containing light resins having a gravity of 14.3 A.P. I., a viscosity of 1700 seconds Saybolt Universal at 210 F. andviscosity-gravity constant of 0.875.

The oil fraction containing the light resins Was then extracted at 100F. With propane in a three stage countercurrent system employing 500volume percent of the propane to produce approximately 17.2% by weightbased on the original charge of still bottoms, a propane insolublefraction having a penetration of 25 at 77 F. and a melting point of 128F. and approximately 17.3% by weight based on the original charge ofstill bottoms of a propane soluble oil having a gravity of 19.3 A. P.I., a viscosity of 446 seconds Saybolt Universal at 210 F. and aviscosity gravity constant of 0.845.

Approximately 40% by Weight of the above resin free oil was blended with60% by weight of the asphaltene fraction containing the heavy resins andthis blend was air blown or oxidized at a temperature of 450-475 F. forabout 2-3 hours to produce an oxidized composited asphalt having amelting point of 221 F., penetrations of 12 at 32 F., 21 at 77 F. and 35at 115 F., a ductility of 1.4 cm. at 77 F., a ash point of 525 F.Pensky-Martens and a weathering life of 106 cycles.

In order to show that the oxidized asphalt produced by deresining thecharging stock resulted in a superior product, a straight Santa FeSprings residuum was oxidized under the same conditions for a period of18 hours. The product resulting from this oxidation had a melting pointof 220 F., a penetration of 24 at 77 F., a ilash point of 490 F. and aweathering life of only 32 cycles in the standard Weather-ometer test.

In order to compare the resins in the asphal- L' tene fraction which wasprecipitated with the butane-iso-pentane solvent mixture with the resinsdissolved by this solvent mixture and contained in the soluble oilfraction, 400 grams of the asphaltene fraction was extracted at room etemperature (77 F.) with 4 liters of 82 naphtha to form an insolubleprecipitate of asphaltenes consisting of 21% by weight and a solublefraction containing the naphtha soluble resins consisting of 79% byweight of the asphalteneresin charge. The naphtha soluble resinspossessed a melting point of 187 F. and penetrations of zero at 32 F.and one at 77 F. The remaining naphtha insoluble asphaltenes were verybrittle having a penetration of zero at 115 F., no

melting point being obtained since at 500 F. they were still unmeltedand started -to decompose.

It will be observed that for determining the melting point, penetration,ductility and flash point, the following methods outlined by theAmerican Society of Testing Materials were used:

Melting point, ball and ring method D-36-26 Penetration 20, page 641.This constant is an indication of the parafnicity or naphthenicity of anoil, a high value representing a high degree of naphthenicity while alow value indicates a relatively greater paraiiinicity.`

The above description of my invention is not to be construed as limitingbut only as illustrative of the invention as many variations may be madewithin the scope of the following claims.

I claim:

1. A process for producing asphalts having air-blown characteristicswhich comprises separating an asphalt residuum into an asphaltenefraction, a resin fraction and an oil fraction and blending said oilfraction with said asphaltene fraction to produce a composited asphaltWhich is substantially free from resins and subsequent'- ly oxidizingsaid blend.

2. A process for producing asphalts having air-blown characteristicswhich comprises separating an asphalt residuum into an asphaltenefraction, a relatively light resin fraction and an oil fraction andblending said oil fraction with said asphaltene fraction to produce acomposited asphalt which is substantially free from light resins andsubsequently oxidizing said blend.

3. A process for producing asphalts having air-blown characteristicswhich comprises mixing an asphalt residuum with a solvent capable ofdissolving oil and light resins but incapable of dissolving asphaltenes,mixing said mixture of light resins and oil with a second solventcapable of precipitating said light resins from said oil to produce anoil fraction which is substantially free from light resins, blendingsaid resin-free oil with said asphaltenes which is substantially freefrom light resins and subsequently oxidizing said blend.

4. A process for producing asphalts having air-blown characteristicswhich comprises mixing an asphalt residuum with a solvent capable ofdissolving oil and light resins but not substantial quantities of heavyresins and asphaltenes, separating the solution of oil and light resinsfrom said asphaltenes and heavy resins, mixing said oil and light resinswith a second solvent capable of precipitating said light resins fromsaid oil, separating a solution of oil and solvent from precipitatedlight resins, blending said oil with said asphaltenes and heavy resinsto produce a composited asphalt which is substantially free from lightresins and subsequently oxidizing said blend.

5. A process as in claim 4 in which said rst named solvent comprises amixture of butane and iso-pentane and said second named solventcomprises propane.

6. A process for producing asphalts having air-blown characteristicswhich comprises mixing an asphalt residuum with a solvent capable ofdissolving substantially resin-free oil but not substantial quantitiesof resins and asphaltenes, separating the solution of oil fromasphaltenes and resins, mixing said mixture of asphalte-nes and resinswith a second solvent capable of dissolving resins from saidasphaltenes, separating the solution of resins from undissolvedasphaltenes, blending said resin-free oil with said asphaltenes toproduce a composited asphalt which is substantially free from resins andoxidizing said blend.

7. A process for producing asphalts having air-blown characteristicswhich comprises mixing an asphalt residuum with a solvent capable ofdissolving substantially resin-free oil but not separating the solutionof oil fromV asphaltenes and resins, mixing said mixture of asphaltenesand resins with a second solvent capable of dissolving light resins butnot substantial amounts of heavy resins and asphaltenes, separating thesolution of light resins from the undissolved heavy resins andasphaltenes, blending said resin-free oil with said asphaltenes andheavy resins to produce a composited asphalt which is substantially freefrom light resins and oxidizing said blend.

8. A composited asphalt produced from an asphalt residuum whichcomprises a blend of asphaltenes and oil, said composited asphalt beingsubstantially free from light resins contained in said asphalt residuumand having air-blown characteristics and weathering life substantiallygreater than an oxidized asphalt produced by air-blowing said asphaltresiduum Without prior substantial quantities of resins'and asphaltenes:

separation of resins therefrom to a melting point substantially the sameas that of said composited asphalt.

9. A composited asphalt produced from an asphalt residuum whichcomprises a blend of asphaltenes and oil, said composited asphalt beingsubstantially free from light resins contained in said asphalt residuumand having air-blown characteristics and a weathering life substantiallygreater than an oxidized asphalt produced by air-blowing said asphaltresiduum without prior separation of resins therefrom to a melting pointsubstantially the same as that of said composited asphalt, saidcomposited asphalt having a melting point of about 221 F., penetrationsof about l2 at 32 F., 21 at 77 F. and 35 at 115 F., a ductility of about1.4 cm. at 77 F., a flash point of about 525 F. and a weathering life ofabout 106 cycles.

DONALD E. CARR.

